Question

Water is to be heated from 15°C to 65°C as it flows through a 3-cm-

internal diameter 5-m-long tube. The tube is equipped with an

electric resistance heater that provides uniform heating throughout

the surface of the tube. The outer surface of the heater is well

insulated, so that in steady operation all the heat generated in the

heater is transferred to the water in the tube. If the system is to

provide hot water at a rate of 10 L/min, determine the power rating

of the resistance heater and heat transfer coefficient.

The properties of water at the bulk mean temperature of Tb =(Ti +

Te)/2 (15 +65)/2 = 40°C are density=992.1 kg/m3

, Cp =4179 J/kg

°C, k = 0.631 W/m °C , Pr = 4.32 , kinematic viscosity= 0.658 ×10-

6 m2

/s

Use following correlation:

Nu=hD/k=0.023 〖Re〗0.8 〖Pr〗n​

Answer 1

Answer:

Cannot determine